The objectives of this research program are 1) to determine the mechanisms by which N. gonorrhoeae attaches to human fallopian tube mucosa and 2) to evaluate methods for blocking this attachment. An assay that makes it possible to quantitate attachment of gonococci and other bacteria to human fallopian tube mucosa has been developed in our laboratory. To determine which gonococcal surface components are involved in attachment to human fallopian tube mucosa we will use this assay to quantitate attachment of gonococcal clones that have different surface components. We will test the competetive effect of purified gonococcal surface components (e.g.,pili, opacity-associated protein) on attachment of gonococci to human fallopian tube mucosa. We will also test the ability of antibody to these purified components to block gonococcal attachment. Serum and various mucosal secretions from volunteers immunized either subcutaneously or intravaginally with a purified pilus vaccine will be tested for their effect on attachment of gonococci to the fallopian tube mucosa. Serum and secretions from patients with naturally occurring gonococcal infections will be similarly studied. Serum and secretions which block attachment of gonococci will be tested to determine whether gonococcal IgA protease alters their blocking ability. The nature and distribution of receptor sites for gonococci on human fallopian tube mucosa will be studied by treating the mucosa with substrate-specific enzymes prior to attachment, by locating specific attachment sites of purified components, and by characterization of receptor-rich fractions of mucosal cell membranes. Finally, we will study a variety of factors that may modulate the number or avidity of receptor sites for gonococci on the fallopian tube mucosal membrane. These studies of gonococcal components and host receptors operative in attachment, and the ability of specific antibodies to block gonococcal attachment should facilitate a targeted approach to testing, as vaccine candidates, those antigens most likely to elicit protective antibodies.